The only problem with a 4" grinder is it will not cut all the way through the wall. Since your only going to do a limited amount of cutting I would get a blade for your skill saw - either abrasive or a diamond blade will do the job. Your going to want good eye and ear protection as this is going to be a dirty, noisy job. The best way to remove brick is to undercut below the section you need to remove. Cut out the bed (horizontal) joint not the brick - it will cut easier. After you get the bed joint cut out attack one brick just above that joint with a chisel or a hammer drill if you have one. The first one is the hardest to get out. Once it is cleared, work your way down the wall along the cut bed joint. When that row is removed go to the row just above it. Use your chisel to remove the head (vertical) joint between two of the brick - take small bites and work from the bottom to the top. Once the head joint is removed, place your chisel on the bed joint just above where you removed the head joint and give it a good smack - it will drop right out. Just use the same technique on subsequent joints and you golden. Remember, the length of the hole will decrease by one brick per row as you go up so you bottom cut need to be long enough to take this into account. Also, in most veneer jobs there will be ties between the structural wall and the masonry. They should not cause you any problems just knock them out of the way. It's not as difficult as it sounds, just take your time and be careful.

Diamond blades are way better than carborundum blades. You can get hundreds of feet of cutting from a diamond blade, the depth of cut doesn't change much, and the cutting is faster.

The carborundum (masonry) blades grind down quickly, you need a stack so you don't run out.

With either, a drizzle water system really improves matters. Otherwise you get blinding clouds of dust. Keep the material damp, soak the mortar joints before slicing them. Drill a relief hole where you change directions so the cut doesn't spider into a crack.

Wear really good eye protection. The dust settles on plastic lens of goggles by static charge, you desperately want to leave them off. Don't-- after getting a carborundum grit removed from my cornea, I learned my lesson- it was painful. A cheap glass diving mask is a good choice.